i have a 470(400) roller cam in the 280's at .050 est. hp around 650 rpm is going to be 7000-7500 it is in a 79 truck and the only headers i can find that fit are 1-3/4 primary i was wanting to run a 2" primary how much will the small tubes hurt hp

there's people out there runnin 10's with 1 3/4 headers. i think 1 7/8 would be ideal, but 2" is over kill unless your sprayin.

Been running low 10`s for years(soon to b 9` based on my 6.22 1/8th)and I run the hooker supercomp 2" od headers spinning to 7000+. These 470`s like rpm`s from what I`m seeing as long as the cam and heads are up to it and my solid roller is an isky .680-.660 lift and 275-280@ .050.

The rule of thumb that I go by is .250 bigger on the primary tube size than the exhaust valve size. So, if you are running a 1.81 exhaust valve then a 2" primary would be about ideal.

Also, I would run a 3.5" collector even if you run a 1 7/8 primary. Talk to Streetwize here on the board. A 3" collector will limit your torque peak on a big motor, which will kill upper end HP.

Years ago I dyno tested a 426 M.W. pump gas street motor on a new DTS engine dyno, the shop did not have a set of dyno headers made up yet so we used a set of Hooker A body 1 7/8 primary tubes about 40 inches to the collectors and 3.5 inch colletors for the first 23 pulls while the shop made up a set of dyno headers. The shop made a set of 2 1/4 primary pipes that where around 25 inches long and 4 inch collectors for there dyno headers, we swap the headers with no other changes and the motor pick up HP all the way thru the RPM range, 3500 to 6500 and lost some torque down low, below 4000 rpm, on the averages the bigger headers made more torqure and HP than the smaller tube set made

what price range does a custom made set of headers run

I've paid anywhere from 800-1500 dollars. They come to your house and build them right on the car.